After installing the B'Stone "half moon" handlebar, I still wasn't happy with the Dahon I'd recently acquired. It was geared too high; the rapid-rise derailleur was fussy and giving me fits; and the plastic pedals were flimsy and uncomfortable. So I resolved to take one more crack at making this bike make sense for me before giving up on it.
1. I ordered a new crankset with a smaller chainring. The loose-bearing bottom bracket came with a spindle that was a touch too short for the new cranks, and the raced bearings were just awful. I overhauled it with loose bearings and a slightly longer spindle from the parts box. Switching from 52t to 48t was a revelation. Also, the cheesy, plastic anti-chain-jump device was no longer needed with chain guards on both sides of the chainring, so I yanked it from the seat tube altogether.
2. I scored some all-metal folding pedals really cheap on eBay. They are sturdier, but no more comfortable than the plastic ones they replaced. I'm not ready to spend $50 on fancy pedals so I'll live with these for awhile.
3. I fine-tuned the stock derailleur, after realizing that installing anything else simply would not work on this frame. I'd have to live with rapid-rise and make it better if I could. The biggest hassle was the placement of the limit screws (really, Dahon? whose bright idea was it to put them where no tool could easily reach without first loosening the derailleur from the hanger hole? Stupid, stupid). Once I sorted it all out, I adjusted it and made it as good as I possibly could. A smaller chainring up front helped make the gears shift more smoothly as well.
4. A small saddlebag to carry everything while still fitting with a folding bike was the last touch.
The only challenge remains how to carry a water bottle on this bike. There are two eyelets on the main tube but the cage would be positioned horizontally; and where would the cage go if I want to fold the bike? I'm looking for a clip-on bottle cage that will fit the handlebar securely until I'm ready to take it off for folding. (Suggestions welcome.)
The test ride around the block was pretty nice -- better hand position, easier and smoother pedaling, and overall better fit have convinced me that this has a place in my stable, and I'm going to keep it.
Some more minor tweaking is probably still in order, and maybe a different saddle; but basically it's all there.